Are Microplastics Toxic to Microbes?

The effects of microplastics on the marine environment is a globally recognised issue. In this investigation the researchers wanted to test standard endpoints given by International Standard Organization (ISO) protocols. Using concentrations of microplastics well above environmentally relevant concentrations (25mg/L) they showed that there were no growth rate or toxicity effects of microplastics on the bacteria Vibrio fischeri and the diatom Phaeodactylum tricornutum.

Unfortunately, there were some inconsistencies in this investigation that are worth noting. The light to dark periods of the experiment are inconsistent ranging form 12-12h light dark to 16-8h light dark period. The mixing tourniquets and bottle types varied with treatment. These inconstancies and the lack of formatting make this a difficult paper to read. It is also strange that microplastics that are almost the size of or larger than the bacteria or algae used are being considered toxins. It is likely that chemicals on the surface of these plastics are more relevant.

Microplastics may not pose a threat to microbes in the ocean and more sensitive endpoints might need to be made for future investigation as highlighted in the study. I think a different approach to this problem would be more effective.

Gambardella, C., Piazza, V., Albentosa, M., Bebianno, M. J., Cardoso, C., Faimali, M., ... & Sendra, M. (2019). Microplastics do not affect standard ecotoxicological endpoints in marine unicellular organisms. Marine Pollution Bulletin, 143, 140-143.